Download Knowing that warm air is less dense than cold air, which do you

Atmosphere
and
Climate
Objective and Key Concepts
How does uneven heating of
Earth's surface result in air
movement?
How are air currents on Earth
affected by Earth's spin?
What are the main wind
belts on Earth?
Global Winds
Wind patterns can be global or local.
There are great wind belts that circle
Earth.
The energy that causes this large
movement of air comes from.... ?
THE SUN!
Unequal Heating of Earth's Surface
Not all areas on Earth
receive the same
amount of energy
from the sun because
it depends on the sun's
angle.
light
Areas near the equator are known as the
tropics. Sunlight strikes Earth's surface
there at a 90 degree angle all yearround. They receive more sunlight, which
causes the land, water, and air at the
equator to be warm.
Near the poles, sunlight strikes Earth at a
low angle. It is spread over more surface
area and it is colder.
Air Density
Warm air rises and cold
air sinks.
Warm air is less dense
than cold air, just like
warm water is less dense
than cold water.
Wind
Knowing that warm air is less
dense than cold air, which do
you think puts more pressure
on Earth?
Air pressure is usually low over the
tropics because it's warm there...
Air pressure is high over colder areas
such as the poles.
This difference in pressure creates wind.
WIND- movement of air from areas of
high pressure to areas of low pressure.
Coriolis Effect
Because the Earth spins,
wind does not move in
perfectly straight lines!
Earth’s Rotation Affects Wind Direction
• Because Earth rotates, scientists are able to tell the
directions wind will flow.
• The Coriolis Effect is the influence of Earth’s
rotation on wind patterns.
• Global winds curve as the Earth turns beneath
them. Winds in the northern hemisphere curve
right and winds in the southern hemisphere curve
left.
Prevailing Wind
Types
Trade winds
polar easterlies
Steady winds
that flow east
to west
Cold winds that
blow from east to
west near the
poles
prevailing
westerlies
Steady winds that
flow west to east
Jet Streams
Near the top of the troposphere is a
narrow band of high winds called the jet
stream. Jet streams flow around Earth
from west to east and influence weather.
They move cold air toward the equator,
and warm air toward the poles as fast as
300 km/hour, and have a strong influence
on our weather.
Sea and Land Breezes
Sea breeze- wind that blows from
the sea to the land due to local
temperature and pressure
differences. Because land warms
faster than water, the differences
in pressure over the warm land
and the cooler water results in a
cool wind that blows from the sea
onto land.
Land Breezes
Land breeze- wind that blows
from the land to the sea due
to local temperature
differences. At night, the land
cools more quickly than the
water. An area of low
pressure forms over the
warm water. Cool air over
land moves toward low
pressure over the water.